1. Field of the Invention
The present invention relates to a light emitting display having an LED lamp as a light source. The term xe2x80x9cLEDxe2x80x9d in this specification means a light emitting diode.
2. Description of the Related Art
It is common to use LEDs in the form of LED lamps which have LED chips (light emitting diodes) enclosed in a mold member.
FIG. 24 is a perspective view showing a conventional LED lamp and FIG. 25 is a schematic cross sectional view of the LED lamp shown in FIG. 24. In FIG. 25, the hatching for expressing the cross section of a mold member is not illustrated.
The conventional LED lamp 2 has an LED chip 5 disposed in a reflector dish 4 mounted to the uppermost end of a cathode 3. The LED chip 5 is electrically connected by a bonding wire 7 to an anode 6. Those components are enclosed in a mold member 8 made of a cylindrical solid form of a transparent material such as epoxy resin.
The top 8a of the mold member 8 of the LED lamp 2 is arranged to form a convex lens of a semi-spherical shape. A pair of lead terminals 9 extending from the cathode 3 and the anode 6 respectively are projected outwardly from the bottom 8b of the mold member 8. The reflector dish 4 has a concave surface thereof provided in an inverted conical shaped recess of the upper side of the cathode 3.
In action, as light of a color attributed to the LED chip material is emitted from the LED chip 5 of the LED lamp 2, it is reflected on the surface of the reflector dish 4 to the front, converged by the lens effect of the top 8a, and radiated to the front. This allows the light to hardly radiate from the bottom 8b and side 8c of the mold member 8. The light radiated from the top 8a is in the form of parallel rays which are slightly dispersed towards the downstream as denoted by the arrows in FIG. 25.
It is known that such an LED lamp as described above is installed in a display body made of a light diffusing resin which comprises a transparent resin doped with a light diffusing material so that light emitted by the LED lamp can radiate from a surface (a light emitting side) of the display body. A characteristic example of the conventional light emitting display is disclosed in Japanese Patent Laid-open Publication (Heisei)1-199513 of the Patent Office in Japan.
However, the conventional light emitting display has a disadvantage that light from the LED lamp is diffused by the action of the light diffusing material as it runs through the display body and when the distance from the top of the LED lamp to the light emitting display surface is short, its diffusion is minimized. This causes the illumination to be varied, brighter in a central region at the top of the LED lamp and darker in the surrounding area.
On the other hand, when the distance from the top of the LED lamp to the light emitting display surface is long, the diffusion of light is relatively satisfied but the intensity of light emitted from the LED lamp is significantly attenuated before reaching the light emitting display surface. Therefore, conventional light emitting display can become dimmed.
Also, as the color of light to be emitted from the light emitting display surface of the conventional light emitting display is strictly determined by the characteristics of the LED lamp as the light source, its variation can hardly be permitted even if desired. It is hence simple and monotonous when a set of the conventional light emitting displays are used for illumination of objects such as in a show-window.
The present invention has been developed in view of the above aspects and its object is to provide a light emitting display which has an LED lamp as the light source and allows its light emitting display surface to illuminate at uniform brightness throughout the area.
It is another object of the present invention, in addition to the above object, to provide a light emitting display which allows its light emitting display surface to illuminate in different colors regardless of the color of light emitted from its LED lamp.
For achievement of the above object, a light emitting display according to the present invention comprises a light emitting display surface made of a light diffusing resin material which comprises a transparent resin doped with a light diffusing material, an LED lamp having an LED chip encapsulated in a mold member made of a light transmissive material and disposed behind the light emitting display surface with its top facing the light emitting display surface, and a light reflective surface disposed at the rear of the LED lamp to face the light emitting display surface, and in which the LED lamp is covered at its top with a light reflective coating. During operation of the light emitting display, light emitted from the LED lamp is reflected on the inner surface of the light reflective coating on the top of the LED lamp, then reflected again on the light reflective surface behind the LED lamp, and radiated outwardly from the light emitting display surface made of the light diffusing resin material and disposed in front of the LED lamp. Accordingly, the diffusion of emitted light can be enhanced so as to allow the light emitting display surface to illuminate substantially at uniform brightness throughout its area.
Also, a light emitting display is provided comprising a display body made of a light diffusing resin material which comprises a transparent resin doped with a light diffusing material, an LED lamp having an LED chip encapsulated in a mold member made of a light transmissive material and embedded in the display body with its top facing a front side of the display body, and a light reflective surface disposed on a rear side of the display body to face the front side, and in which the LED lamp is covered at its top with a light reflective coating.
Accordingly, the light emitting display can be reduced in the thickness and also allow the display body to illuminate substantially at uniform brightness throughout its surface.
Moreover, a light emitting display is provided comprising a casing with a front plate made of a light diffusing resin material which comprises a transparent resin doped with a light diffusing material, an LED lamp having an LED chip encapsulated in a mold member made of a light transmissive material and mounted in the casing with its top facing the front plate, and a light reflective surface disposed behind the LED lamp on the casing to face the front plate, and in which the LED lamp is covered at its top with a light reflective coating. Accordingly, the pitch between any two adjacent LED lamps can be increased so as to allow the display body to illuminate substantially at uniform brightness throughout its surface.
Alternatively, the light reflective coating covering the top of the LED lamp may be made of a film of an opaque paint. This permits the light reflective coating to be formed easily and efficiently.
Preferably, the paint coating may be a film of a white color paint. This allows the light emitting display surface to illuminate at higher brightness. In addition, the LED lamp can hardly be identified when viewed from the outside.
Alternatively, the LED lamp may have a white-light LED chip and its mold member is covered at the outer surface, excluding at least the top, with a light transmissive tinted coating.
Preferably, the LED lamp may have a white-light LED chip encapsulated in a mold member made of a light transmissive, tinted material. This allows the illumination of a favorable intermediate tone of color which is hardly realized with any conventional LED chip.
Each of the above light emitting displays may be modified with a plurality of the LED lamps which are classified into at least two different types for emitting two different colors of light and arrayed in a combination at equal intervals of a distance or pitch. Accordingly, when the LED lamps are connected to a controller circuit for switching on and off each color group of the LED lamps, the light emitting display can shift the display of illumination from one color to another.
Alternatively, each of the above light emitting displays may be modified with a plurality of the LED lamps which are classified into a red color LED lamp, a green color LED lamp, and a blue color LED lamp and arrayed in a predetermined arrangement. This allows the light emitting display to produce a white color of light in addition to a desired combination of any two colors.
Preferably, each of the above light emitting displays may be modified so that a plurality of the LED lamps, each lamp being a three-color LED lamp having a red color LED chip, a green color LED chip, and a blue color LED chip encapsulated in a single mold member, are provided and arrayed at equal intervals of a distance or pitch. Accordingly, the number of LED lamps can be decreased as compared with each LED lamp having a corresponding LED chip.